Saturday, May 16, 2020

Does the shape of the acromion matter?

Acromial morphology is not associated with rotator cuff tearing or repair healing

These authors sought to determine whether acromial morphology
(1) could be measured accurately on magnetic resonance images (MRIs) as compared to computed tomographs (CTs) as a gold standard,
(2) could be measured reliably on MRIs,
(3) differed between patients with rotator cuff tears (RCTs) and those without evidence of RCTs or glenohumeral osteoarthritis, and
(4) differed between patients with rotator cuff repairs (RCRs) that healed and those that did not.

They measured coronal, axial, and sagittal acromial tilt; acromial width, acromial anterior and posterior coverage, and glenoid version and inclination on MRI corrected into the plane of the glenoid.

They determined accuracy by comparison with CT via intraclass correlation coefficients (ICCs).
To determine reliability, these same measurements were made on MRI by 2 observers and ICCs calculated.
They compared these measurements between patients with a full-thickness RCT and patients aged >50 years without evidence of an RCT or glenohumeral osteoarthritis.
They then compared these measurements between those patients with healed RCRs and those with a retorn rotator cuff on MRI at least 1 year from RCR. Only those patients without tendon defects on postoperative MRIs were considered to be healed.

In a validation cohort of 30 patients with MRI and CT, all ICCs were greater than 0.86. In these patients, the inter-rater ICCs of the MRI measurements were >0.53.
In the RCT group of 110 patients, there was greater acromial width. Although the acromion was wider in shoulders with RCTs, the difference of 0.1 mm may have no clinical significance.
In these patients there was significantly less sagittal acromial tilt than in the comparison group of 107 patients.

At a mean follow-up of 24 months, 84 patients (76%) had healed RCRs.
There was no association between healing and any of the measured morphologic characteristics of the acromion.

The authors concluded that their findings call into question subacromial impingement due to native acromial morphology as a cause of rotator cuff tearing. Furthermore, acromial morphology, critical shoulder angle, and glenoid inclination were not associated with healing after RCR. As a result they concluded that this study did not support lateral acromioplasty.

Comment: There is now substantial literature questioning the significance of the shape of the acromion in the pathogenesis of cuff tears.
In addition there is now substantial literature questioning the value to the patient of surgical modification of the acromion. See, for example, this link.


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